Method and apparatus for positioning substrates

ABSTRACT

A method and apparatus for positioning substrates is provided. The substrates are typically semiconductor wafers that require centering on a mounting location within a process module and orientation of a notch, flat or perimeter interruption to a known rotational position. A robot arm transfers wafers from a source to the process module. A camera is provided adjacent a path of travel of the robot arm to scan the wafers as they pass thereover. A grayscale analysis determines the centroid, or other reference point, of the wafer and the location of the notch or flat. The path of travel of the arm is altered to account for misalignment of the centroid/reference point from a known location. Data related to the rotational offset of the notch or flat relative to a known standard location is also obtained. The wafer can be rotated to position the notch or flat at a desired standard position using a rotator mounted on the robot arm or at a remote site.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for aligning androtationally orienting substrates and more particularly to asemiconductor wafer processing system with improved wafer handlingcharacteristics.

BACKGROUND OF THE INVENTION

The production of etched semiconductor wafers for use in microcircuitchips typically employs large process module systems. Semiconductorprocess modules form part of a large grouping of components that areusually located in a clean room environment. A clean room is an isolatedenvironment in which the introduction of dust and other foreign matteris strictly controlled. Only by maintaining such control can a highquality semiconductor product be produced. The high level ofenvironmental control makes clean room space extremely expensive. Sincethe majority of semiconductor processing equipment must be locatedwithin the floor space of the clean room, the size of that equipmentbecomes a significant cost consideration.

A conventional semiconductor wafer processing facility, according to theprior art, is detailed in FIG. 1. The facility in this example is acluster tool 20. A variety of arrangements and organizations offacilities are in use. In particular, the cluster tool includes acentral transport or handling module or platform 22 that is surroundedby modules that perform operations on the wafers. In this example,unprocessed wafers 24 are stored in a vacuum cassette elevator 26 thatmoves a stack of wafers upwardly to provide new wafers as needed. Arobot arm 28 having articulating joints 30 and 32 connecting armsegments 33 and 35 is used to handle wafers 24 within the facility 20.An end effector 34 engages each wafer 24 and withdraws it (double arrow36) from the vacuum cassette elevator 26 as needed. The arm 28 movesabout its pivoting base 38 to access each of the facility modulesaccording to a preprogrammed sequence or "recipe."

Wafers 24 are processed to include etched or deposited surfaces byprocess modules that perform specific tasks. A typical cluster tool caninclude two to four process modules. Wafers are often shuttled betweenone process module and another to undergo multiple process steps. Priorto entry of a wafer, into a process module it is common practice toalign and orient the wafer into a standard position. Most wafers arecircular in perimeter outline, but each may include a notch, flat orother "interruption" at an arbitrary location along its perimeter. Thisnotch or flat serves to provide a standard rotational reference pointfor further processing.

When wafers 24 are stacked in the cassette 26, they are not generallyoriented so that all notches or flats are similarly positioned. Inaddition, wafers are not always accurately centered on the end effector34 following retrieval from the cassette 26. Hence, without performingprior alignment, each wafer may enter a particular process module withits own unique rotational orientation and centering. Proper processinggenerally necessitates that wafers be centered in the various processmodules. Thus they must be centered relative to the end effectors thatplace wafers into the modules. Rotational orientation should also remainconstant, particularly during the photolithography step of the processso that patterns are stacked over one another in the properrelationship. It is also desirable to maintain a known rotationalorientation when wafers are periodically inspected for non-uniformities.An inspection usually entails a survey of the processed surface withrespect to the notch or flat. If some portion of the processed surfaceincludes a non-uniformity or defect, then this may suggest that aparticular process module should be serviced. Accordingly, the positionof the notch or flat relative to the mounting location 41 and 43 of therespective process module 40 and 42 must be known to derive the sourceof the non-uniformity. Hence, prior to insertion of wafers 24 intoprocess modules 40 and 42, the wafers are fed (arrow 44) to an alignmentmodule 46 that places each wafer in a properly centered and rotatedposition with respect to the robot arm.

During the alignment step, the end effector 34 lays each wafer atop aspinner or capstan 48 having a series of vacuum ports 50, or otherfriction-generating devices that retain the wafer on the spinner 48. Alifter having four pins 52 can be employed to carefully lower the waferonto the spinner once the end effector is located over it. FIG. 2illustrates the positioning of a typical wafer 24, in an unalignedstate, on the spinner 48. The wafer's center 54 is offset from thedesired center 56. Likewise, the notch 58 is offset from the desiredrotational positioning of the notch (shown in phantom). This rotationaloffset is represented by an angle θ. The spinner 48 rotates the wafer 24as an edge detector 60 scans the perimeter 62 of the wafer. Changes inposition of the detected perimeter edge during rotation are used toderive the eccentricity of the wafer center 54 relative to the spinnercenter 56. An edge detect circuit 66 calculate the degree ofeccentricity based upon the detected changes.

Based upon signals from a robot arm controller 68, the wafer isperiodically lifted by the robot arm 28 to reposition the wafer so thatits center 54 is aligned with the spinner center 56. Once the wafer isally centered, the edge detector 60 is then focused upon the notch 58.The wafer is spun until the notch is found. The spinner 48 rotates thewafer so that the notch is positioned at a desired rotation orientation.Following the centering and orienting procedure, the wafer is liftedfrom the spinner 48 using, for example, the pins 52 and reengaged by thearm end effector 34. The end effector then transports the wafer (arrow68) to the process module 40. At this time, the end effector enters themodule and places the wafer at a precise, preprogrammed location forsemiconductor processing. Following processing, the wafer is typicallymoved by the arm (arrow 70) to a receive indexer 72. The wafer may berealigned in the alignment module each time a further process isperformed. Thus, if the wafer is subsequently moved to the secondprocess module 42, it may, first, make a return trip to the alignmentmodule 46.

In some facilities, process modules include elaborate entrance and exitload locks (ELL's and XLL's) each having individual arms with individualalignment units. Clearly, a great deal of space is occupied by the needfor dedicated alignment modules and mechanisms. As noted above, thiswaste of precious clean room floor space to provide alignment devicesadds substantial costs to the process.

It is, therefore, an object of this invention to provide a method andapparatus for aligning and rotationally orienting substrates, such assemiconductor wafers, that omit complex alignment modules andmechanisms. This method and the related apparatus should increase theoverall process speed for manufacturing wafers, but should still providedesired information on the precise orientation and alignment ofindividual wafers. The method and apparatus should also provide improvedtracking of wafers as they move through a processing facility.

SUMMARY OF THE INVENTION

This invention provides a method and apparatus for aligning/centeringand rotationally orienting substrates, particularly for use insemiconductor wafer processing facilities, that overcome thedisadvantages of the prior art. A camera, interconnected with agrayscale processing unit scans each wafer to locate its relativeposition and its associated perimeter notch or flat. This data is usedto effect alignment and rotational orientation of the wafer as it entersselected process modules in the facility. As a result, a separatealignment module can be omitted, and rather than centering each wafer onthe facility's manipulator arm, the arm is reoriented based upon theactual position of the wafer on the arm. As such, the arm proceeds to aprocess module along a modified path of travel.

According to one embodiment, an apparatus for positioning substratesprovides a source of substrates and a manipulator having an end effectorfor engaging the substrates at the source. The end effector can be partof an arm that moves the substrates to locations remote from the source.One of the locations can be a process module that processes substrates.Such a process can include semiconductor etching or deposition. Theprocess module has at least one mounting location for mountingsubstrates thereon. A camera is provided. The camera generates an imageof a substrate when the substrate is located on the end effector andwhile the end effector is positioned adjacent the camera. By "adjacent,"it is meant under, over, or otherwise located in o position in which thecamera can view the wafer. A sensing processor is operativelyinterconnected to the camera. The sensing processor determines theposition of the centroid or another reference point of the substrate andcompares the position of the reference point with a known position ofthe mounting location. The end effector position relative to themounting location is also known, and the robot arm travels along a knownpath to the mounting location. Thus, the end effector can be adjusted toaccount for variations in the centering of the wafer. And theseadjustments affect the final positioning of the end effector when itreaches the mounting location. A manipulator control processor, that isoperatively interconnected with the sensing processor moves the endeffector while compensating for a difference between the known positionand the centroid (or other reference point) of the substrate so thatwhen the end effector is moved automatically to the mounting location inthe process module, the wafer's centroid is placed over the mountinglocation's center.

The apparatus can further include a perimeter interruption locator thatscans for a notch, flat or other interruption along the perimeter of thesubstrate. The locator compares a sensed perimeter interruption to aknown angular location and uses this data to derive an offset angle θ. Amemory can be provided to store the angle θ for future use. The angle θcan also be employed to physically rotate the substrate using a rotatormounted on either the end effector or at a remote, freestandinglocation. The manipulator can be a robot arm that is located in acluster tool handling module. The arm can also be located in an entranceload lock, that services as a process module.

According to another embodiment, a method for positioning substrates isprovided. Substrates are retrieved from a source of substrates. An endeffector of a manipulator engages the substrates. The end effector islocated adjacent to a camera unit. An outline shape of the substrate isretrieved as an image. Using the image, a centroid or other referencepoint of the substrate is determined and the position of the referencepoint relative to a known location is also determined. The differencebetween the position of the wafer's reference point and the knownlocation is calculated and stored as an adjustment factor. The endeffector is, thus, moved to a remote location along a predetermined paththat is changed to account for the adjustment factor.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages of the invention willbecome more clear with reference to the following detailed descriptionas illustrated by the drawings in which:

FIG. 1, already described, is a schematic plan view of a cluster toolfor processing substrates, including an alignment module according tothe prior art;

FIG. 2, already described, is a more-detailed schematic plan view of awafer located on the spinner of the alignment module of FIG. 1;

FIG. 3 is a schematic plan view of a semiconductor wafer processingfacility, including a mechanism for aligning and rotationally orientingwafers according to one embodiment of this invention;

FIG. 4 is a schematic plan view of an end effector having a spinneraccording to an alternate embodiment of this invention;

FIG. 5 is a schematic plan view of an entrance load lock (ELL) for usewith a process module, having a mechanism for aligning and rotationallyorienting wafers according to another alternate embodiment of thisinvention; and

FIG. 6 is a flow diagram of a process for aligning and rotationallyorientating substrates according to this invention.

DETAILED DESCRIPTION

FIG. 3 illustrates a semiconductor processing facility according to anembodiment of this invention. The processing facility is organized as acluster tool 100 with a central wafer handling module 102 surrounded bya series of process modules. Elements that are like those described forthe prior art cluster tool 20 of FIG. 1 are given like referencenumbers. In particular, a pair of process modules 40 and 42 are locatedon adjacent sides of the handling module 102. Additionally, a centrallylocated robot arm 28 is provided. The robot arm, like that of FIG. 1,uses a pantograph-style arm arrangement with a pair of driving joints 32for swinging arm segments 33 and 35. The arm segments are, themselves,joined by articulating joints 30. The arm 28 is mounted on a swivelingbase 38. The powered joints 32 enable the end effector 34 to moveforwardly and rearwardly (double arrow 104). The base 38, similarly,rotates (curved arrow 106) to move the end effector about the module102. In this embodiment, the end effector 34 can be made movableupwardly and downwardly (perpendicularly to the plane of the page) byproviding an elevator drive (not shown) to the swiveling base 38 or asimilar lifting mechanism acting upon the arm 28 or the end effector 34.

According to this embodiment, a camera unit 108 having a camera lens 110is located adjacent the vacuum cassette elevator 26. The exact locationof the camera unit 108 can be varied depending upon the configuration ofthe facility. It is desirable that it be located in an area that isalong the natural path of travel of the arm or adjacent thereto, tominimize extraneous movements of the robot arm 28 from a direct path oftravel between modules. In this embodiment, the camera is mounted on thesurface of the handling module 102 so that wafers pass "over" the camerato be scanned. It is contemplated that the camera can be mounted overthe module 102 or at a remote point so long as the camera can view thewafer at some point along its path of travel. While the term passing"over" is used to describe the scanning of the wafer, that term shouldbe taken to include scanning of the wafer by the camera at any relativepositioning, including "over," "under," "aside" or "adjacent."

The camera unit 108 comprises a conventional solid-state CCD, orequivalent video camera, having an objective view point or lens sizesufficient to scan the entire surface of a wafer 24 at once.Alternatively, the camera can be located so that it scans only part ofthe wafer, but derives an image of the entire wafer as it passesthereover. However, in a moving scan application, additional scanningsoftware (described generally below) is required.

The camera unit 108 is interconnected with a wafer centroid andnotch/flat sensing circuit 112. The operation of this circuit is alsodescribed further below. In summary, it is a commercially availableimage processor circuit or software package that uses a conventionalgrayscale analysis of the viewed wafer passing over the camera unit 108.The sensing circuit 112 determines the center or "centroid" of the waferand the orientation of the notch or flat on the wafer perimeter usingknown centroid calculation methods. Again, while the wafer centroid islocated according to this embodiment, it is expressly contemplated thatthe sensing circuitry can identify any reference point or group ofpoints (such as the perimeter or a portion of the perimeter) on thewafer to determine its relative position. For example the sensingcircuit or routine can scan for an arc of the wafer perimeter and storedate representing a relative location of the arc. Thus while "centroid"is used herein, it shall be taken broadly to include any reference pointor points on the wafer from which a position of the wafer can bediscerned.

The sensing circuitry 112 is interconnected with the robot arm controlcircuit 114 which has been modified to interpret data from the sensingcircuit 112. The robot arm control 114, which can be integrated into thehandling module 102, is operatively connected with the robot arm 28 sothat the control 114 directs movement of the robot arm 28 about themodule 102.

Reference may now also be made to the flow diagram of FIG. 6 which setsforth the alignment sequence for a wafer according to this embodiment.In this embodiment, the robot arm 28 is programmed to move so that theend effector withdraws a wafer 24 from the cassette (block 113) andpasses over the camera unit 108 (block 115) as it moves (arrow 118) tothe process module 40. The camera unit 108 scans the wafer 24 as itrests on the end effector 34. To ensure proper scanning, the arm 28 canslow down or stop briefly while the end effector is adjacent the cameraunit 108. Conversely, a quick-scanning camera can vitiate the need fordelay as the wafer passes over the camera unit 108. The profile of thewafer 24 is scanned by the camera unit and the data of the visual imageis digitized by conventional processes and transmitted as a data streamto the wafer centroid and notch/flat sensing circuit 112. This sensingcircuit 112 can be implemented in hardware, or part of a softwareprocessor routine. It can be part of the existing handling module 102arm controller or can be an added component. The sensing circuit 112performs a grayscale analysis of the viewed image (block 117).

According to this embodiment, the grayscale analysis is performed whenthe robot arm end effector 34 has reached a predetermined known locationrelative to the camera unit 108. The triggering of the camera unit 108and sensing circuit 112 can be linked to the robot arm control circuit114 which tracks the position of the end effector 34 as it moves alongits path. When a location corresponding to the location of the cameraunit is identified, the camera unit 108 and sensing circuit 112 aretriggered. In performing the resulting grayscale analysis, the sensingcircuit 112 differentiates between darkened areas, representing thespace occupied by the wafer 24 and lighter areas, representing the spaceoccupied by the area outside the perimeter of the wafer 24. In someembodiments, an appropriate light-colored background can be providedabove the camera to generate a contrast difference. The perimeteroutline of the wafer, including the notch or flat, are translated into aseries of coordinate values and the coordinate values are compared tothe desired location of a wafer 24 when the end effector 34 is locatedat the predetermined known location relative to the camera unit 108. Thecalculation can include a derivation of the scanned wafer's centroid (orother reference point) relative to the desired center point. Calculatingthe difference between the actual scanned wafer centroid and the desiredcenter point, an X and Y-component transformation is obtained (block119). This value is stored. The sensing circuit 112 also determines thelocation of the flat or notch of the wafer by identifying adiscontinuity in the perimeter. It is contemplated that most perimetersof wafers are circular, but other shapes having relatively regularoutlines are also contemplated. The rotational position of thediscontinuity relative to the camera unit 108 is determined. This valueis stored as an angle θ (block 123). Note that each wafer in a set to beprocessed can be numbered or identified and that the data relative tothe X and Y-transformation and angle θ can be permanently storedrelative to that wafer's identifier.

As further detailed in FIG. 3, subsequent to scanning, the wafer ismoved along the path (arrow 118) to the process module 40. The robot arm28 adjusts its movement path to account for the X and Y-transformationso that the wafer is placed within the process module with a correctionfactor that leaves it accurately centered at the mounting location 41within the process module (block 121).

No further scanning of the wafer at the process module is required, allvariation in wafer centroid positioning has been accounted-for with thetransformation, and the end effector travels to a known location in theprocess module subject to the correction factor. In the basic embodimentdescribed above, the rotational orientation of the wafer 24 is notchanged. The angle θ, rather, is stored and used later as a correctionfactor (block 123). In such an embodiment, the angle θ is used as areference for determining the actual rotational orientation of theprocessed surface relative to the notch or flat. As noted above,inspection of wafers generally occurs only periodically (once every 12or 24 hours) to ensure that the process unit is performing as expected.Subsequent to processing, the wafer can be transferred to anotherprocess module, such as adjacent process module 42 or, as shown, can betransferred back to the receive cassette 72 (see arrow 119). If furtherprocessing is undertaken, the robot arm 28 can pass back over the cameraunit 108 to ensure that alignment is maintained. Alternatively,additional camera units (not shown) interconnected with the sensingcircuit 112 can be provided at other strategic positions on the handlingmodule 102.

In some processes, it is desirable to provide a positive rotationalorientation to wafers as they are moved between steps. FIG. 4 details anend effector 120 that can be used in conjunction with the robot arm 28shown and described in FIG. 3. In this embodiment, the end effector 120includes an outer frame 122 having support bearings 124. The outer frame122 is formed as a C-shape with an open center 126 and a channel 128.This enables the end effector to pass over a spinner, capstan or otherfreestanding support. An inner frame 130 with inner support bearings 132is also provided in this embodiment. The inner and outer frames can beconnected by appropriate underlying braces (not shown) to maintain aconstant coaxial relationship. Between the inner and outer frames 122and 130, respectively, is positioned a circular base member 134 thatrotates (curved arrow 136) relative to the inner and outer frames 122and 130. The base 134 can include a frictional surface 138 or portsinterconnected with a vacuum source (not shown) to maintain the wafer innon-slidable contact with the base 134. The base 134 can be formed witha raised surface so that the frames 122 and 130 do not drag upon a wafersurface when the wafer rests upon the end effector 120. The base 134rotates in response to a motor 140. The motor 140 is mounted upon thebase support bracket 142 according to this embodiment. However, themotor 140 can be mounted anywhere along the end effector or remote fromthe end effector. When mounted remote from the end effector, the motoris interconnected with the base by appropriate drive shafts and powertransmission components of conventional design (not shown).

The motor 140 can comprise a stepper motor or servo that enables therotational position of the base 134 relative to the frames 122 and 130to be ascertained at any time and accurately manipulated. The motor 140is interconnected with a rotator control circuit 144 that can beimplemented as a hardware control circuit or, alternative as a softwareroutine. The rotator control circuit 144 is, itself, interconnected withthe wafer centroid and notch/flat sensing circuit 112 described withreference to FIG. 3. Data related to the rotational angle θ istransmitted to the rotator control, which rotates the base 134, via themotor 140. The translation of the base is directed in a clockwise orcounter-clockwise direction for an angular distance equal to θ. Thevalue θ can be supplied to the system as a positive or negative value toinstruct the motor to move in either a clockwise or counter-clockwisedirection, respectively.

Referring again to FIG. 6, the rotation of the wafer by the end effector120 is illustrated as an optional step block 150). The rotation canoccur prior to arm translation, while the wafer is still adjacent thecamera unit 108. The camera unit 108 can be instructed to rescan thewafer to ensure proper rotation. Subsequent to rotation the wafer istranslated (block 152) to the designated process module where it isproperly aligned within the module using the X-Y transformation valuesdetermined by the wafer sensing circuit 112. Alternatively, the spincommand can be transmitted to the end effector when the wafer is locatedadjacent the process module. A spin can occur at any time during theprocess so long as it occurs before the wafer is disengaged from the endeffector 120. The spinner can also operate in conjunction with signalsfrom the robot arm control circuit 114 to spin the wafer as it movesinto other process modules so that it always enters a given processmodule in a predetermined rotational orientation.

The aligning and rotational orienting process described according tothis invention is not limited to facilities organized as cluster tools.FIG. 5 illustrates an alternate embodiment in which wafers 24 areretrieved from a send indexer 200 for placement in an entrance load lock202 that services a process module 204. The entrance load lock (ELL) 202includes automatically operated gates 206 and 208 that enable a vacuumto be formed at selective times within the entrance load lock prior tointroduction of wafers 24 into the process module 204. An entrance loadlock arm assembly 210 extends at selected times through the port 206 toretrieve wafers 24 from the send indexer 200. The arm 210 includes twoarm segments 212 and 224 joined at an articulating shoulder 216. The endeffector 218 that engages wafers 24 is fork-shaped according to thisembodiment. A drive motor 220 controls the arm 210 to move it about theentrance load lock. Various conventional linkages (not shown) can beprovided to move each of the two arm segments 212 and 214 in acoordinated manner. For the purposes of this description, it is assumedthat the linkages are all operatively interconnected with the controlbase 222 of the arm 210. The control base 222 is, itself, interconnectedwith the entrance load lock control circuit 224. The control circuit 224can be a hardware or software-based processor and can be interconnectedwith the overall facility control system. In this embodiment, wafers 24are retrieved by the arm 210 and moved (arrow 226) adjacent an entranceload lock spinner unit 228. In this embodiment, a camera unit 230 isprovided adjacent the spinner unit 228. The camera unit 230, including acamera lens 232, can be provided in any location over which the endeffector 218 can pass. As described in preceding embodiments, the cameraunit 230 can be constructed from a variety of conventional componentsand is positioned so that it views the disk fully when the disk ispositioned adjacent thereto.

A four-pin lifter unit comprising four pins 234 is positioned around thecapstan 236 on the spinner unit 228. The capstan 236 can includeconventional vacuum holes for firmly engaging a wafer. In operation,wafers 24 are removed from the send indexer 200 and passed along thepath 226 to the capstan 236. The camera unit 230 analyzes the centroidand notch location of the wafer 24 using the wafer centroid andnotch/flat sensing circuit 240. The sensing circuit 240 operates in amanner similar to that described with reference to FIG. 3. In otherwords, a grayscale analysis is used to determine the location of thewafer centroid and notch or flat. The centroid data is translated into Xand Y-values and transmitted to the arm control circuit 224. The arm isthen moved to compensate for the difference in the centroid positionfrom a desired location. In this embodiment, the four pins 234 thenraise the wafer, giving clearance for the end effector 218 to move awayfrom the wafer 24 and capstan 236. The pins 234 then lower the wafer 24onto the capstan 236 in a centered alignment. The capstan 236 rotates(curved arrow 244) based upon commands from the spinner control circuit246. The spinner control circuit 246 operates after receiving the value0 from the wafer centroid and notch/flat sensing circuit 240. The waferis now aligned and properly oriented. The four pins 234 again lift thewafer, enabling the end effector 218 to pass thereunder. The endeffector 218 locates itself at a predetermined position relative to thecapstan 236 so that, when the pins 234 again lower the wafer onto theend effector, the wafer is accurately positioned and oriented relativelyto the end effector 218. The end effector is then moved along the path(arrow 250) through the port 208 into the process module 204. The endeffector 218 deposits the wafer within the process module at a knownmounting location 251, corrected for centroid misalignment.

The simplified alignment structure of this embodiment allows the receivecassette 252 to be positioned aside the send cassette 200. The exit loadlock (XLL) 254 is adapted to move wafers from the process module (arrow256) and then, at a right angle into the receive cassette 252 (arrow258). Prior art exit load locks typically discharge in a straight linefrom the process module to the receive cassette since a complicatedshuttle arm and lifter/spinner arrangement is located in the spaceoccupied by the send and receive cassettes 200, 252 of this embodiment.The prior art send cassette is located substantially further away fromthe entrance load lock that the cassette 200 of this embodiment. Hence,the omission of elaborate alignment mechanisms has enabled substantialcompaction of the facility's footprint in the clean room.

It is contemplated that the four pins 234 can be omitted and that theend effector 218 can be constructed so that it raises and lowers thewafer onto the capstan 236 itself. Whenever the end effector is out ofengagement with the wafer, it is free to move to a new orientation toaccount for misalignments of the wafer. It is also contemplated that theend effector of the ELL arm described herein can include an integralspinner, such as that shown and described with reference to FIG. 4.Hence, only a camera unit need be located within the entrance load lock202. However, as shown and described in FIG. 5, a separate spinner canbe incorporated into any of the embodiments described herein. Such aspinner can be instructed to rotate based upon data derived from thecamera's grayscale analysis of the location of the notch or flat.

The foregoing has been a detailed description of preferred embodiments.Various modifications and additions can be made without departing fromthe spirit and scope of this invention. For example, while semiconductorwafers are used as substrates in the foregoing embodiments, anysubstrate having a known perimeter can be processed according to thisinvention. Additionally, a variety of process facility configurationscan be adapted to utilize the aligning and orienting processes describedherein. When desirable, several cameras can be utilized in a singlefacility and separate analyses for each camera can be made. Accordingly,this description is meant to be taken only by way of example and not tootherwise limit the scope of this invention.

What is claimed is:
 1. A method for positioning substrates comprisingthe steps of:providing a source of substrates having a generallycircular perimeter with an interruption along the perimeter; retrievinga substrate from the source of substrates including engaging thesubstrate with an end effector of a manipulator the end effectorincluding a spinner for rotating the substrate when the substrate is inengagement with the end effector; locating the end effector adjacent acamera unit with the substrate located in engagement with the endeffector wherein the camera views the substrate as it is located on theend effector; retrieving an image of a shape of the perimeter of thesubstrate with the camera including positioning the substrate withrespect to the camera so that the camera acquires an image ofsubstantially an entire area of the substrate; determining, from theimage of the entire area of the substrate, a reference point within theperimeter of the substrate and a position of the reference pointrelative to a known location of the end effector as the image isretrieved; determining an angular value θ based upon an angular offsetof the interruption from a known standard position; calculating amovement adjustment factor, while the substrate is positioned on the endeffector based upon a difference between the location of the referencepoint and the known location; moving the end effector to a substrateprocessing location along a predetermined path of movement, the pathbeing modified based upon the adjustment factor so that the substrate isplaced in the processing location with the perimeter aligned in adesired alignment; and rotating the substrate by the angle θ so that thesubstrate is placed in the processing location in a desired rotationalalignment while the substrate is located on the end effector by rotatingthe spinner with which the substrate is engaged.
 2. The method as setforth in claim 1 for the comprising storing the value θ in conjunctionwith an identifier for the substrate.
 3. The method as set forth inclaim 1 wherein the step of determining includes acquiring an angularalignment notch on the perimeter of the substrate.
 4. The method as setforth in claim 1 further comprising applying a semiconductor processingstep to the substrate at the remote location.
 5. The method as set forthin claim 1 wherein the step of determining includes performing agrayscale analysis of image data transmitted from the camera unit andresolving location values relative to a perimeter of the substrate. 6.The method as set forth in claim 1 wherein the reference point includesthe centroid of substrate and the known location is located at theremote location and comprises a center of a substrate mounting location.7. An apparatus for positioning substrates comprising:a source ofsubstrates each having a perimeter with an interruption along theperimeter; a manipulator including an end effector that engages asubstrate at the source of substrates and that moves the substrate onthe end effector in a predetermined orientation to a substrate processmodule for processing substrates remote from the source; wherein theprocess module includes a mounting location for mounting substratethereon in a desired orientation; a camera unit located along a path ofmovement of the end effector between the source and the process module,the camera having a field of view within the path so as to view thesubstrate as the substrate is engaged the end effector, and the camerabeing constructed and arranged to acquire an image of substantially theentire area of the substrate while the substrate is engaged by the endeffector and to thereby; a sensing processor operatively interconnectedto the camera, the sensing processor being constructed and arranged todetermine, based upon the image of substantially the entire area of thesubstrate, a reference point of the substrate and to establish aposition of the end effector when the image is acquired, the sensingprocessor being further constructed and arranged to compare a locationof the reference point with a known position of the end effector whenthe image is acquired and being further constructed and arranged tosense a rotational location of the interruption to derive an offsetangle θ with respect to a desired rotational orientation of theinterruption; a manipulator control processor, operativelyinterconnected with the sensing processor, the manipulator controlprocessor being constructed and arranged to move the end effector whilethe substrate is positioned thereon to compensate for a differencebetween the known position and the reference point so that the endeffector places the substrate in the desired orientation at the mountinglocation of the process module; and a rotator mounted on the endeffector and in engagement with the substrate while it is positioned onthe end effector, the rotator being operatively connected with thesensing processor, the rotator being constructed and arranged to rotatethe substrate by the offset angle θ to the desired rotational locationas the end effector is moved to the mounting location so that thesubstrate is placed at the mounting location in the desired rotationalorientation.
 8. The apparatus as set forth in claim 7 further comprisinga memory operatively interconnected with the locator for storing a valuefor θ.
 9. The apparatus as set forth in claim 7 wherein the interruptioncomprises an annular alignment notch located on the perimeter of thesubstrate.
 10. The apparatus as set forth in claim 7 wherein the cameracomprises a solid state CCD camera.
 11. The apparatus as set forth inclaim 7 wherein the process module comprises a semiconductor processmodule and the substrate comprises a semiconductor wafer.
 12. Theapparatus as set forth in claim 7 wherein the manipulator comprises acluster tool robot arm mounted within a handling module, and wherein theprocess module is located adjacent the handling module.
 13. Theapparatus as set forth in claim 12 further comprising a another processmodule for processing substrates, located adjacent the handling module.14. The apparatus as set forth in claim 12 wherein the manipulatorcomprises an entrance load lock arm mounted in an entrance load locklocated at an entrance to the process module.
 15. The apparatus as setforth in claim 7 wherein the reference point includes a centroid of thesubstrate.
 16. An apparatus for positioning substrates in a substrateprocessing facility having a process module with a mounting location,the apparatus comprising:a robot manipulator including an end effectorfor engaging and moving substrates to the mounting location along aprogrammed path from a source location to the mounting location remotefrom the source location, the end effector further including a rotatingsurface mounted thereon that rotates substrates thereon to a desiredrotational orientation; a camera unit located with a field of view inline with the programmed path, the field of view being arranged toacquire an image of substantially the entire area of the substrate whilethe substrate is engaged by the end effector and the end effector islocated at a known location; an image processor, interconnected with thecamera unit, that determines, based upon the image, the location of acentroid of the substrate and a location of a perimeter interruption onthe substrate; and a controller that adjusts the programmed path basedupon a translation from the known location to an adjusted location inview of a location of the centroid, while the substrate is positioned onthe end effector, based upon a difference between the location of thecentroid at the predetermined time and a desired location of thecentroid at the predetermined time and that further rotates the rotatingsurface to position the interruption at a desired rotational orientationwith respect to the mounting location.